package com.hmdp.utils;


import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate ){
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();

        redisData.setData(value);

        //在原有的基础上加上多少秒
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));

        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R,ID>R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback, Long time, TimeUnit unit){
        String key = keyPrefix + id;
        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在这里是判断是否 是null值和"" 如果是 则输出false
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在，直接返回
            return JSONUtil.toBean(shopJson, type);
        }
        //判断命中的是否是("") 上面已经判断是否为空了
        // 如果不为空则执行这一句,
        //如果这里是""会执行此句 此处的空值来自当数据库为空值时缓存的
        if (shopJson != null) {

            return null;
        }

        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);

        //5.不存在，返回错误
        if (r == null){

            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);

            return null;
        }

        //6.存在，写入redis
        //stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(r),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        this.set(key,r,time,unit);

        return r;
    }

    public <R,ID> R queryWithLogicalExpire(
            String keyPrefix,ID id,Class<R> type,Function<ID,R> dbFallback, Long time, TimeUnit unit){
        String key = keyPrefix + id;
        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否命中未命中 返回空
        if(StrUtil.isBlank(shopJson)){
            //3.不存在，直接返回
            return null;
        }
        //4.命中，需要json反序列化对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);

        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);

        LocalDateTime expireTime = redisData.getExpireTime();

        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {

            //5.1 未过期直接返回店铺信息
            return r;
        }
        //5.2已过期 需要缓存重建

        //6.缓存重建
        //6.1获取互斥锁
        //6.2判断是否获取锁成功

        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);

        //6.3成功 开启独立线程实现缓存重建
        if (isLock){

            CACHE_REBUILD_EXECUTOR.submit(() ->{
                try {

                    //查询数据库
                    R r1 = dbFallback.apply(id);

                    //写入redis
                    this.setWithLogicalExpire(key,r1,time,unit);


                    //this.saveShop2Redis(id,20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    unLock(lockKey);
                }
            });
        }

        //6.4返回过期的商铺信息

        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    /**
     * 获得锁
     * @param key
     * @return
     */
    private boolean tryLock(String key){

        //利用setnx命令来设置锁，此命令不能修改已经存在的key
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);

        //不能直接写拆箱，因为有可能出现空指针 用hutool工具把Boolean 转化为boolean
        return BooleanUtil.isTrue(flag);
    }

    /**
     * 释放锁
     * @param key
     */
    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }
}
